1. Field of the Invention
The present invention relates to a video-signal processing device connectable to an electronic endoscope, and more particularly relates to a video-signal processing device that intervenes between an electronic endoscope and peripheral equipment such as a television (TV) monitor, a video tape recorder, a printer, a video-image processing computer, and so on.
2. Description of the Related Art
The described electronic endoscope comprises a flexible conduit and a video processor to which the flexible conduit is detachably joined.
The flexible conduit has an objective lens system provided at the distal end thereof, and a solid state image sensor such as a CCD (charge-coupled device) associated therewith. An object to be photographed is focused by the objective lens system, as an optical image, on a light receiving surface of the CCD image sensor. The optical image is converted into analog image-pixel signals by the CCD image sensor, and the analog image-pixel signals are successively read out of the image sensor by a CCD driver circuit.
Also, the flexible conduit has an optical guide provided therewithin, and the optical guide terminates at a light-emitting end face of the distal end of the flexible conduit. The video processor includes an optical guide provided therein. When the flexible conduit is joined to the video processor, one end of the optical guide of the video processor is connected to a proximal (base) end of the optical guide of the flexible conduit.
The video processor of the electronic endoscope also has a light source, and a collective lens system associated therewith. Light rays emitted from the light source are focused on the other end face of the optical guide of the video processor by the collective lens system. Thus, the front area of the distal end of the flexible conduit is illuminated by the light rays emitted from the light-emitting end face of the optical guide of the flexible conduit.
For reproduction of a photographed image as a color image, for example, an RGB field sequential type color imaging system is introduced in the electronic endoscope. Namely, a rotary RGB color filter is placed in a position intervening between the light source and the inner end face of the optical guide of the video processor, and the RGB color filter is rotated at a given frequency of rotation. An object to be photographed is thereby sequentially illuminated by red light rays, green light rays, and blue light rays. Thus, a red optical image, a green optical image, and a blue optical image are focused on the light receiving surface of the CCD image sensor at given time intervals.
Analog color-image-pixel signals successively read from the CCD image sensor by the CCD driver circuit are fed to the video processor, which processes the analog color-image pixel signals to thereby produce a color video signal. Usually, the video processor of the electronic endoscope is connected to a medical TV monitor designed to ensure electrical security, and a photographed image is reproduced on the medical TV monitor on the basis of the color video signal fed from the video processor. In this context, "electrical security" designates both confidentiality and protecting a patient from stray current on the signal line.
Also, the electronic endoscope may be connected to a consumer TV monitor at medical site for reproduction of a photographed image thereon. However, in general, a consumer TV monitor is not designed to ensure electrical security.
On the other hand, a user may want to connect an electronic endoscope to other peripheral equipment (such as a video tape recorder, a printer, an image-processing computer and so on) other than a TV monitor. To this end, the video processor of the electronic endoscope is arranged to output at least two kinds of color video signals. However, in this case, of course, the peripheral equipment are not designed to ensure electrical security.
Further, the user may wish to connect the electronic endoscope to a peripheral remotely located from where the electronic endoscope is used. For example, at a large hospital of more than two buildings, there may be a case where a color video signal must be fed from the electronic endoscope used in a room of a first building to a peripheral location in a room of another building. In this case, the video signal is preferably fed as a digital video signal from the electronic endoscope to the peripheral equipment, because an analog video signal is susceptible to attenuation.
Nevertheless, the feeding of the digital video signal to the remote peripheral equipment is not expedient, because an expensive (parallel) signal cable having a plurality of signal lines, corresponding to a bit number of the digital video signal, must be laid therebetween.
Furthermore, when a photographed image is reproduced on a peripheral such as a television (TV) monitor, a video tape recorder, a printer, an image-processing computer, and so on, the user may wish to add messages or comments concerning the reproduced image thereto.